how long has the US had the greatest military

The U.S. has generally been considered the world’s top military power for about 80 years , starting around the end of World War II in 1945. That said, its military roots go back much further, to 1775 with the Continental Army.

Why 1945 is the usual benchmark

Before World War II, other countries often had stronger land armies or overall military influence at different moments. After 1945, the U.S. emerged as a global superpower with unmatched spending, worldwide bases, and strong capabilities across land, sea, air, and later space and cyber.

Earlier military history

If you mean the age of the U.S. military itself, that starts in 1775 , when the Continental Army was created during the American Revolution. The modern armed forces trace their origins to those Revolutionary War institutions.

Simple answer

• Greatest military power: roughly since 1945.

• Military existence: since 1775.

If you want, I can also turn this into a quick timeline of how U.S. military dominance developed.